1. Field of the Invention
The present invention relates to radio systems, and more particularly, to radio systems providing alternate channels for tuned channels.
2. Background Art
The Radio Data System (RDS) specification allows a radio station to send a side-band stream of data along with the audio broadcast on a frequency modulated (FM) frequency signal. In the side-band provided data, the broadcaster can include a list of alternate frequencies (AF), which are other FM frequencies that carry broadcasts that are the same as that of the original radio station. A radio receiver can be configured to use the AF list information to automatically switch to a different frequency when the radio receiver goes out of range from the original radio station. For example, the radio receiver may be carried by an automobile or person. As the automobile or person moves, the radio receiver may move out of range of the original radio station, requiring the radio receiver to be tuned to one of the alternate frequencies.
However, when the AF list contains more than one alternate station, it is not known which of those alternate stations is preferable for selection. For example, it may not be known which of the alternate frequencies is receivable in the new location of the radio receiver. The radio receiver may be forced to cycle through the list of alternate stations, attempting to receive a signal at each alternate frequency, to find a receivable alternate frequency. This can take time, and thus may be an inconvenience to the radio listener.
Thus, what is needed are improved ways of selecting alternate frequencies in a radio receiver for carrier signals that provide alternate frequencies.